Shelf



FIG. 1 is a perspective view.

FIG. 2 is a front view.

FIG. 3 is a rear view.

FIG. 4 is a left or right side view, the two being mirror images of each other.

FIG. 5 is a top view; and,

FIG. 6 is a bottom view. 

The ornamental design for a shelf, as shown and described. 